The functions of the Cryopreservation and Embryo Derivation Core are: A) to expeditiously transfer mutant mice created by the Osaka group in Japan to the La Jolla group. B) to rederive frozen embryos shipped from La Jolla to Osaka. C) to generate ES cell-derived chimeric mice for the establishment of knockout mice by microinjection of ES cells into mouse blastocysts and implantation. D) to submit mutant mouse strains to the MMRRC for distribution to the scientific community. Generation of mouse models have made major contributions to recent advances in the field of innate immunity. In the proposed project to investigate anti-viral immune responses by both forward and reverse genetics, close collaboration between the La Jolla group (conducting mouse forward genetics) and the Osaka group (conducting mouse reverse genetics) will be essential for success. We will exchange mutant mice and will study them in parallel using different viruses. We will also analyze signaling pathways based on the outcome of experiments in which ENU-induced mutations and knockout mutations are combined. A rapid and safe means of exchange, circumventing quarantine and allowing quick assessments, will be provided by this Core. The Core will also be responsible for the microinjection of ES cells into mouse blastocysts and re-derivation from the embryos for generating knockout mice. Finally, the Core will also send mutant mouse strains generated in Osaka to the MMRRC for distribution to the scientific community, permitting accelerated research in many laboratories worldwide.